Contrasting Diversity Patterns of Crenarchaeal, Bacterial and Fungal Soil Communities in an Alpine Landscape

International audienceBackground: The advent of molecular techniques in microbial ecology has aroused interest in gaining an understanding about the spatial distribution of regional pools of soil microbes and the main drivers responsible of these spatial patterns. Here, we assessed the distribution of crenarcheal, bacterial and fungal communities in an alpine landscape displaying high turnover in plant species over short distances. Our aim is to determine the relative contribution of plant species composition, environmental conditions, and geographic isolation on microbial community distribution. Methodology/Principal Findings: Eleven types of habitats that best represent the landscape heterogeneity were investigated. Crenarchaeal, bacterial and fungal communities were described by means of Single Strand Conformation Polymorphism. Relationships between microbial beta diversity patterns were examined by using Bray-Curtis dissimilarities and Principal Coordinate Analyses. Distance-based redundancy analyses and variation partitioning were used to estimate the relative contributions of different drivers on microbial beta diversity. Microbial communities tended to be habitat- specific and did not display significant spatial autocorrelation. Microbial beta diversity correlated with soil pH. Fungal beta- diversity was mainly related to soil organic matter. Though the effect of plant species composition was significant for all microbial groups, it was much stronger for Fungi. In contrast, geographic distances did not have any effect on microbial beta diversity. Conclusions/Significance: Microbial communities exhibit non-random spatial patterns of diversity in alpine landscapes. Crenarcheal, bacterial and fungal community turnover is high and associated with plant species composition through different set of soil variables, but is not caused by geographical isolation

Changes in root-associated microbial communities are determined by species-specific plant growth responses to stress and disturbance

International audienceThe diversity changes in the rhizosphere microbial communities of four grass species submitted to a stress (drought) and/or a disturbance (defoliation) were examined in a full factorial common garden experiment. The diversity of bacterial and fungal communities was determined using Single Strand Conformation Polymorphism (SSCP) and multivariate analyses of variance were performed to test for the effect of experimental factors on microbial beta diversity, i.e. the variation of microbial community composition among pots. Plant species identity contributed the most to microbial beta diversity with 22% of the total variance explained and this effect was stronger for fungi than for bacteria. The effect of defoliation was significant for fungal communities, and more pronounced for plant species that exhibited an increased root biomass following defoliation. Drought had a higher effect on bacterial beta diversity, and this was particularly noticeable for plant species that were the least able to tolerate water shortage. Our results showed that both plant species identity and characteristics of plant growth response captured the plant-mediated effects on microbial diversity. They illustrate the biotic cascade between plants responding to a changing environment and the dynamics of rhizosphere microbial communities

Le Maroc au présent. D'une époque à l'autre, une société en mutation

Le Maroc est probablement l’un des pays d’Afrique du Nord et du Moyen Orient les plus étudiés par les sciences sociales et humaines. Motivée par la diversité objective du pays, cette faveur n’en demeure pas moins ambiguë, en ce qu’elle a contribué à consacrer l’antinomie tradition/modernité. À rebours de ce cliché, Le Maroc au présent expose plusieurs facettes des tensions qui traversent la société marocaine et montre qu’elles ne sont ni figées ni subies par les gens. En multipliant les approches en sciences humaines et sociales, cet ouvrage examine, notamment à partir d’observations de terrain, les transformations qui se sont produites ce dernier quart de siècle, à tous les niveaux. Pour donner à connaître, du plus près possible, le Maroc d’aujourd’hui, l’ouvrage propose une variété de regards croisés, souvent personnalisés, sur les processus sociaux, dans leurs expressions les plus variées. En cela, Le Maroc au présent se veut beaucoup plus un ouvrage d’exploration qu’un simple livre de synthèse. De par la pluralité disciplinaire des contributeurs et la diversité des terrains explorés, il est un état de la recherche sur le Maroc contemporain, fait à partir du Maroc